In this 12-part series, I've urged all readers to play the following six auctions (no interference, of course) as natural and game forcing:

1-2; 1-2; 1-2; 1-2; 1-2; 1-2.

If responder does not have enough for a 2/1 GF, he can pass, respond on the one-level, or raise opener.

The 1NT response shows up to 12 points. Some people play it as "forcing," others as "semi-forcing." You must decide which way you wish to play it with your partner. If "semi-forcing," the opener will pass with a flat minimum.

The 1NT "forcing" or "semi-forcing" response is used only after a 1 or 1 opening (not after 1).

If the 1NT response is treated as "Semi-Forcing," the opener can pass. However, he would pass only if he has a balanced minimum (like 5-3-3-2 and 12 or 13 points). If opener does pass, then 1NT will be the final contract. The downside of playing 1NT semi-forcing (passable) is that sometimes 1NT will be the final contract when the responder had something else in mind. Responder to 1 would bid 1NT with each of these hands:

A 4 2 K 2 Q 10 8 7 J 10 8 7 or

2 A J 10 8 7 6 4 3 Q J 7 6.

In the first case, responder was hoping to bid 3 on his second turn to show a 3-card limit raise. On the second hand, he was hoping to bid 2 next to play there. It turns out there might be no "next" as 1NT will be the final contract if opener passes with his flat minimum. This is the downside of "1NT semi-forcing." On the upside, if opener does bid again after 1NT semi-forcing, he bids completely naturally--just as in "Standard." His rebids in a new suit "promise" 4 or more cards (no bidding 3-card minors). Also, 1NT will often be the right contract when responder has a flat hand opposite opener's flat hand.

Notes:

In this series, I have given my preferences. There are other treatments out there. Be aware that some partnerships use the following exceptions to what is in this series:

1) They play that Opener's "Reverse" shows extras (as opposed to not promising extras)

2) They play that Opener's rebid on the 3-level shows extras (as opposed to not promising extras)

3) They play that Opener's rebid of his major does not show six cards--it is the default rebid (as opposed to suggesting 6).

4) They play that Opener's rebid of 2NT guarantees stoppers in all unbid suits (as opposed to not guaranteeing).

5) They play that Opener's jump rebids show extras (as opposed to just a solid suit).

6) They play opener's immediate jumpshifts as natural and strong (as opposed to a Splinter raise).

7) Not everyone plays 2/1 as 100% GF (they allow the partnership to stop in a partial if responder rebids his suit).

9) Responder's second bid of 3NT needs defining ("extras" or a fast-arrival sign-off.)

I have tried to give what I think are the mainstream treatments--and also what I believe is best. What I've spelled out is probably the simplest and easiest to play/remember. I have listed 1-9 above, just so you are aware that there has been no standardization (as this is being written in the year 2011) yet of all 2/1 GF systems. By reading these 12 articles I'd feel confident in saying you are 90% of the way there.